Topical carbonic anhydrase inhibitors IV: Relationship between excised corneal permeability and pharmacokinetic factors.

Ethoxzolamide (1) and two analogues, representing a hydroxyethoxy and a hydrogen substitution on the 6-position of the benzene ring (2 and 3), were applied to rabbit eyes using a topical infusion method designed to provide a constant rate into aqueous humor. Statistical-moment theory was applied to the topical infusion data to describe disposition of each compound within the rabbit eye. For each analogue, it was possible to compare the corneal absorption rate constant (ka), aqueous humor elimination rate constant (k10), disposition mean residence time (MRTd), apparent steady-state volume of distribution (Vdss), and total ocular clearance (Qe). In vivo ocular ka values were related to maximum in vitro corneal penetration rates determined across excised rabbit corneas. In particular, 2 had a much longer residence time and a slower clearance than 1 and 3, which may be responsible for its ability to lower intraocular pressure when dosed topically to the rabbit eye, whereas 1 and 3 show no activity.